Differential Anomalous X-ray Scattering from an Amorphous Polymer Electrolyte: [PPO]xZnBr2

Abstract

Differential anomalous X-ray scattering (DAS) and extended X-ray absorption fine structure (EXAFS) were used to determine the local structure surrounding the ions in amorphous polymer electrolyte complexes of poly(propylene oxide) and ZnBr 2 : [PPO] 6 ZnBr 2 and [PPO] 16 ZnBr 2 . On the basis of our results, we propose that ZnBr 2 dissociates to form mainly ZnBr 4 2- and Zn(O) 4 2+ , where (O) is an ether oxygen on a PPO chain. This observation is contrasted with aqueous ZnBr 2 , where ZnBr 2 , ZnBr 3 - , and ZnBr 4 2- are all observed in the estimated proportions of 2:4:3, respectively. This paper describes the DAS method and its application to structure determination in a multicomponent, amorphous system. In systems with n components, where one or more of the species is a heavy atom, DAS reduces the scattering intensity from a weighted sum of n(n+1)/2 partial structure factors to a sum of partial structure factors which only include the heavy atom of interest